The structure and function of the cytoskeletal protein myosin will be studied at the genetic, molecular and biochemical levels in the budding yeast Saccharomyces cerevisiae and the fission yeast Schizosa charomyces pombe. These organisms have been chosen for analysis because they are simple unicellular eukaryotes with well established genetics and are easily manipulated by sophisticated techniques of molecular biology. The proposed study centers on three areas of investigation: firstly, the cloning and DNA sequence analysis of the myosin genes in these organisms; secondly, the determination by Northern hybridization of the number and sizes of the mRNA transcripts produced; and thirdly, the isolation, purification and characterization of the expressed myosins both structurally and functionally. This study will establish a system for work in the cell biology and molecular analysis of these cytoplasmic myosins. In future studies mutant myosins can be created by site-specific mutagenesis and returned to the yeast genome for analysis. As myosin appears to be ubiquitous amongst eukaryotes and is differentially expressed during development in mammalian organisms, this study of the myosin molecule ultimately will contribute to our understanding of cellular functioning and differentiation.